Is the stock S7 Edge charger safe to use with an older S4?

[Noodle Eater]

I have an S4 laying around that I use for random stuff now that I've upgraded to the S7 Edge. Am I able to use the charger that came with my new phone to charge the S4? I noticed it got a lot hotter than normal.

I also noticed my new phone gets really hot when charging, I'm guessing this is just the fast charge doing its thing?

 

[Ramer84015]

I have an S4 laying around that I use for random stuff now that I've upgraded to the S7 Edge. Am I able to use the charger that came with my new phone to charge the S4? I noticed it got a lot hotter than normal.

I also noticed my new phone gets really hot when charging, I'm guessing this is just the fast charge doing its thing?

I'm not so sure about that. I use wireless fast charging and even leaving my phone on the charging pad all night, it's barely warm to the touch. If it's getting really hot, you may want to have it looked at and/or replaced while under warranty.